The above-identified copending application describes a method whereby pyrophoric P.sub.4 -containing material can be converted to a substantially less pyrophoric form while it is under a suitable blanketing layer of a nonflammable fluid (e.g., water or inert gas) with an oxygen-containing gas such as air, pure oxygen, or mixtures thereof. The action of the oxygen on the P.sub.4 -containing material while it is being blanketed with the nonflammable liquid reduces the pyrophoric nature of the P.sub.4 -material over time rendering it substantially less pyrophoric. Details concerning how the conversion of the pyrophoric P.sub.4 -material to a less pyrophoric form can be conducted in accordance with the invention described in that copending application are incorporated herein by reference.